Re: [Libunwind-devel] 10% lost unwind traces on x86-64?

[Arun Sharma]

On Mon, Mar 8, 2010 at 7:24 AM, Lassi Tuura <address@hidden> wrote:

> - Suspiciously large fraction of failures occur at (function+0), i.e. at 
> function entry address.
>

This has been discussed before:

http://thread.gmane.org/gmane.comp.lib.unwind.devel/284/focus=296

There is a patch in that thread that might be useful for solving this.

For the remaining problems, I'd suggest:

* Trying a new libc

If the problem goes away, someone added missing unwind info.

* Examining readelf -wf for the code in question

This is a manual step. If you can prove that the compiler modified the
stack pointer and forgot to generate unwind info, try testing a more
recent compiler.

* Signal frames libunwind doesn't understand

I haven't seen weird calling conventions in practice yet. But signals
are of two types:

* IP points to the instruction *after* the one that triggered the signal
* IP points to the instruction *before* the one that triggered the signal

libunwind doesn't distinguish between the two yet.

 -Arun